With practically and high speed industrial type sewing operation, and as is even more pronounced when dealing with heavy-weight work pieces, there are two inherent problems that adversely affect the sewing operation. The first problem is concerned with guarding and positioning the needle with respect to the lower stitch forming instrumentalities so as to prevent damage to the needle and/or lower stitch forming mechanism. The other problem is concerned with the prevention of excessive needle heat.
With regard to the first situation, needle guarding is necessary because as the needle reciprocates, it passes in close proximity to the loop taker element of the lower stitch forming mechanism. On its return stroke, the needle throws out a loop of thread which is seized by the loop taker element forming the desired stitch. In the event that the needle should become bent or deflected by irregularities in the material or the like, the needle may be displaced from its normal path which could result in skipped stitches of the needle striking the loop taker element and, thus, resulting in a scoring of the loop taker element or a breakage of the needle. The second problem, excessive heat of the needle, is caused by friction between the needle and the cloth. Excessive heat build-up may result in melting of the workpiece in certain instances or the breaking of the thread passing through the needle eye and will reduce considerably the ability of the needle to pierce the workpiece. The problem is accentuated because as the needle becomes duller, more heat is created as the needle attempts to pierce the material being worked on.